What is denormalization and when to use it

Short answer

Denormalization is the deliberate introduction of redundant data into a normalized schema to reduce joins and improve read performance.

How it works

Instead of storing customer_name only in the customers table, you might duplicate it in the orders table to avoid a join on order reports. This trades write complexity and storage for read speed.

When to use it

• Read-heavy workloads where join costs are unacceptable.
• Reporting and analytics databases where data changes infrequently.
• When using caching or materialized views is insufficient.

Tips

• Maintain denormalized data with triggers, application logic, or batch ETL processes.
• Document the redundancy and the synchronization strategy clearly.

Common issues

• Updates become more complex because multiple copies must stay synchronized.
• Inconsistent denormalized data causes misleading reports if synchronization fails.r